The present invention relates to homogeneous, single-phase liquid detergents. More specifically, liquid compositions comprising an anionic detersive surfactant, a nonionic detersive surfactant, a source of magnesium ions, and an alkanolamine are prepared in a manner which avoids undesirable phase separation.
Heavy-duty, built laundry detergents have historically been provided in the form of granules. More recently, however, it has been recognized that excellent detergency performance can be secured using unbuilt detergents comprising a mixture of detersive surfactants and materials such as alkanolamines. The advent of such compositions has made it possible to provide heavy-duty laundry detergents in liquid form.
Liquid detergent compositions offer several advantages over solid compositions. For example, liquid compositions are easier to measure and dispense into a laundering liquor. More importantly, liquid compositions are especially useful for direct application to heavily soiled areas on fabrics, after which the pre-treated fabrics can be placed in an aqueous bath for laundering in the ordinary manner.
Typical heavy-duty liquid detergents contain substantial amounts of nonionic surfactants which help provide grease and oil removal from synthetic and blend fabrics. However, many important types of detersive nonionic surfactants tend to form a separate phase in liquid compositions containing substantial amounts of electrolytes. Of course, phase separation (presumably, a manifestation of the so-called "salting-out" effect) is unacceptable when formulating homogeneous liquid detergents. Accordingly, the presence of electrolytes, especially water-soluble polyvalent inorganic salts, is usually avoided when preparing such compositions.
Preferred heavy-duty liquid detergents will also contain a substantial amount of one or more synthetic detersive anionic surfactants. The anionic surfactant helps provide improved cleaning performance over a broad spectrum of soils and fabric types. Moreover, the anionic surfactant provides the suds levels desired by most users of such products.
As noted above, alkanolamines, especially triethanolamine, are often used in heavy-duty liquid detergents to adjust pH and to provide a substantial increment of additional cleaning power.
It is well known in the detergency arts that certain polyvalent metal cations (especially when used in combination with synthetic anionic surfactants) can contribute substantially to detergency performance. Accordingly, it is desirable to incorporate a source of such cations into a detergent composition. In particular, calcium and magnesium salts of various types are useful detergency boosters, and salts such as magnesium acetate, the calcium and magnesium halides, magnesium sulfate, calcium and magnesium hydroxide, and the like, have been suggested for this purpose, especially in the formulation of heavy-duty granular detergents.
It has now been discovered that calcium and magnesium salts cannot be used in random fashion when preparing homogeneous heavy-duty liquid detergents since phase separation will occur. However, compositions prepared in the manner disclosed herein are stable, homogeneous liquids.
The co-pending application of Payne, et al., entitled LIQUID DETERGENT COMPOSITION, Ser. No. 592,009, filed June 30, 1975, now U.S. Pat. No. 3,998,750 discloses homogeneous liquid detergents containing magnesium salts and which can contain small, non-detersive amounts of alkanolamines.
The co-pending application of Hellyer, et al., Ser. No. 538,618, filed Jan. 6, 1975 abandoned in favor of application Ser. No. 634,389, also now abandoned in favor of application Ser. No. 669,531, filed on Mar. 23, 1976, discloses liquid detergent compositions which contain, inter alia, a source of magnesium ions and a mixture of surfactants, including anionics and amine oxides.
It is an object of this invention to provide homogeneous, heavy-duty liquid detergents which contain magnesium salts, alkanolamines, anionic surfactants and nonionic surfactants at levels which provide superior detergency performance.